1. Field of the Invention
The present invention involves a hammer-bit assembly for pneumatically drilling a borehole in the earth and more particularly, such assemblies which have eliminated the need for a mud motor or other motor to drive the hammer-bit.
2. Information Disclosure Statement
Numerous systems have been developed for boring the earth and there is significant patent literature on the subject. The following patent references illustrate the state-of-the-art and show numerous types of drilling systems which involve complex assemblies:
U.S. Pat. No. 5,139,094 to Bernhard Prevedel et al. involves methods which are provided for controlling the direction of a borehole drilled by a downhole motor, including the steps of positioning downhole adjustable bent housing and near-bit stabilizer in the drill string, adjusting the bent housing from its normally straight condition to its bent condition to effect borehole curvature, and using the stabilizer in its undergauge condition to enhance the inclination. The Measurements are made from which the inclination with respect to the vertical and the azimuth can be determined and telemetered uphole for processing, display and recording. Preferably the directional measurements are made at two locations, one below the bent point and one above it. These two sets of measurements can be compared to confirm the bend angle and to obtain a definition of the orientation of the plane of the bend angle so that the drilling path can be accurately controlled. The use of this invention eliminates having to superimpose rotation of the deflected drill string in order to drill straight ahead because the bend angle can be eliminated by downhole adjustment.
U.S. Pat. No. 4,991,667 to Robert D. Wilkes, Jr. et al. describes a hydraulic drilling method and apparatus in which the drilling fluid itself is utilized to control the direction in which a hole is bored in the earth. The drilling fluid is discharged through a plurality of forwardly facing nozzles which are inclined at different angles about the axis of the drill head, and the drilling fluid is selectively applied to the nozzles by a rotatable valve member to control the direction in which the hole is cut.
U.S. Pat. No. 4,948,925 to Warren Winters et al. involves an apparatus and method for orienting a collar on a fluid conducting conduit, such as a drill string, includes an orifice through the wall of the conduit and a latch assembly for latching the collar to the conduit. The latch assembly allows fluid communication through the orifice and rotates the collar when the conduit is rotated in a first direction about the longitudinal axis of the conduit. The latch assembly unlatches the collar from the conduit, prevents fluid communication through the orifice, and allows the conduit to rotate relative to the collar when the conduit is rotated in a second, opposite direction. Also included are apparatus and method for rotationally orienting a fluid conducting conduit including an insert connectable inside the conduit so that the insert is rotatable with the conduit; a flow passageway extending through the insert; a piston bore in the insert; a piston, reciprocally mounted in the piston bore, for reciprocating between the ends of the piston bore, the piston restricting flow through the flow passageway and creating a fluid pressure increase on the upstream side of the insert when the piston is in a restricted position in the piston bore; and a barrier mass for blocking the pilot passageway in a selected rotational position of the pilot passageway and conduit in order to increase the fluid pressure at the downstream end of the piston bore and move the piston to the restricted position in the piston bore.
U.S. Pat. No. 4,890,682 to Robert N. Worrall et al. involves a jarring apparatus which is used for vibrating a pipe string in a borehole. The apparatus thereto generates at a downhole location longitudinal vibrations in the pipe string in response to flow of fluid through the interior of said string.
U.S. Pat. No. 4,862,974 to Tommy M. Warren et al. describes a downhole drilling apparatus for use with an undergauge drill bit and comprises a downhole drilling motor which includes a housing and means for rotating the drill bit relative to the housing about an axis of rotation. The apparatus also comprises stabilizers connected to the housing for stabilizing the drill bit, and it further comprises cutters connected to the housing for cutting a borehole wall created by passage of the drill bit wherein the cutters extend radially outwardly relative to the axis of rotation to a greater extent than does the drill bit. A drilling assembly including such a drilling apparatus and a method of drilling a substantially vertical borehole in an earthen formation utilizing such an apparatus are also disclosed in the invention.
U.S. Pat. No. 4,834,193 to Curtis E. Leitko, Jr. et al. describes an earth boring apparatus which has a pneumatically operated earth boring tool, a flexible conduit or drill pipe connected to the tool and to a source of pneumatic fluid. The tool has an earth boring member and a reciprocally movable hammer positioned in the tool to apply a percussive force. A valve assembly in the flexible conduit or drill pipe substantially adjacent to the tool between the tool and the source of pneumatic fluid to the tool. The valve assembly has a pneumatic pressure-operated valve which is operable in response to the pressure of pneumatic fluid in the flexible conduit or drill pipe to be opened to permit flow of pneumatic fluid to the tool at a predetermined operating pressure to transmit an initial pulse of pneumatic fluid to initiate operation of the hammer. The valve is kept open at a lower pressure than that required to open it. One form of the valve is a pressure operated valve, spring-loaded toward closed position, which opens at a first predetermined pneumatic pressure permitting flow to said tool and closes at a second, substantially lower, pneumatic pressure. Another form of the valve means has a valve, spring-loaded toward closed position, which opens in response to pneumatic conduit pressure, and spring loaded ball detents or a pneumatic pressure operated latch to secure the valve in an open position. The latch and valve are operated to closed position at a lower pressure.
U.S. Pat. No. 4,790,394 to Ben W. O. Dickinson, III et al. involves a hydraulic drilling apparatus and method suitable for use in a variety of applications including the drilling of deep holes for oil and gas wells and the drilling of vertical, horizontal or slanted holes, drilling through both consolidated and unconsolidated formations, and cutting and removing core samples. The drill head produces a whirling mass of pressurized cutting fluid, and this whirling fluid is applied to a discharge nozzle to produce a high velocity cutting jet. The cutting action is enhanced by abrasive material in the drilling fluid. The direction of the borehole is controlled by controlling the discharge of the drilling fluid either in side jets directed radially from the distal end portion of the drill string which carries the drill head or in a plurality of forwardly directed cutting jets.
U.S. Pat. No. 4,754,819 to Thomas B. Dellinger describes a wellbore drill string which is formed from a plurality of sections of drill pipe interconnected at tool joints with a drill bit at its lower end. A drilling fluid is circulated down the drill string and up the annulus between the wellbore and the drill string. A plurality of annulus reducers located at spaced-apart positions along the drill string impart a cyclical pumping action to the flowing drilling fluid. During drilling, the drill string is axially reciprocated and an extension capability to the drill string maintains continuous weight on the drill bit.
U.S. Pat. No. 4,694,913 to William J. McDonald et al. is directed to a guided earth boring tool. Long utility holes, for gas lines, electrical conduit, communications conduit and the like, may be bored or pierced horizontally through the earth, particularly under obstacles, such as buildings, streets, highways, rivers, lakes, etc. Such holes may be bored by an underground drilling mole (underground percussion drill) supported on a hollow drill rod and supplied with compressed air through the rod to operate an air hammer which strikes an anvil having an external boring face, preferably constructed to apply an asymmetric boring force. The drill rod is operated by a drill rig on the surface or recessed in special pit for horizontal drilling and provides for addition of sections of pipe or hollow rod as the boring progresses. The asymmetric boring force causes the boring path to curve and, when straight line drilling is needed, the drill rod is rotated to counteract the asymmetric boring force. An alternative boring tool utilizes an expander supported on a solid or hollow drill rod and having a base end supported on and larger in diameter than the rod and tapering longitudinally forward therefrom. It may have a uniform extension protruding a short distance forward. The tool penetrates the earth upon longitudinal movement of the drill rod.
U.S. Pat. No. 4,632,191 to William J. McDonald et al. involves a steering system for percussion boring tools for boring in the earth at an angle or in a generally horizontal direction. The steering mechanism comprises a slanted-face nose member attached to the anvil of the tool to produce a turning force on the tool and movable tail fins incorporated into the trailing end of the tool which are adapted to be selectively positioned relative to the body of the tool to negate the turning force. The fins are constructed to assume a neutral position relative to the housing of the tool when the tool is allowed to turn and to assume a spin inducing position relative to the housing of the tool to cause it to rotate when the tool is to move in a straight direction. Turning force may also be imparted to the tool by an eccentric hammer which delivers an off-axis impact to the tool anvil. For straight boring, the tail fins are fixed to induce spin of the tool about its longitudinal axis to compensate for the turning effect of the slanted nose member or eccentric hammer. When the fins are in the neutral position, the slanted nose member or the eccentric hammer will deflect the tool in a given direction. The fins also allow the nose piece to be oriented in any given plane for subsequent steering operation.
U.S. Pat. No. 4,408,670 to William N. Schoeffler involves a sub assembly to be inserted between a drill string and a bit has a stabilizer sleeve to engage the walls of a bore hole and hold a first cam against rotation. A second cam is fixed to a drill holder at the lower end of the assembly and is driven in rotation by a rotary driving member extended through the assembly. The cams interengage so that relative rotation between them applies periodic impacts to the drill holder.
U.S. Pat. No. 2,641,445 to Robert E. Snyder describes a rotary impact drill intended for connection to a rotatable drill stem. It includes a rotary member adapted to be connected to the drill stem for movement therewith, a bit receiving member, a fluid coupling connected between the rotary member and the bit receiving member to rotate the latter at a speed less than that of the rotary member, whereby relative rotation between the members is produced. Also included are a hammer, which is reciprocally mounted on one of the members to deliver impacts to the bit receiving member, and cam means operatively connected between the relatively rotating members and to the hammer to reciprocate the latter when relative rotation exists between the drill stem and the bit receiving member.
U.S. Pat. No. 2,371,248 to John J. McNamara describes a well drill having a supporting body with a passageway extending downwardly from the top thereof, whereby a fluid under pressure may be supplied to the drill, a water turbine supported by the body, a by-pass conduit having its inlet end in the passageway and adapted to direct a portion of the supplied fluid past the turbine, other conduit means connected to the passageway to direct the remainder of the fluid to the turbine whereby to effect rotation thereof and a discharge conduit means extending down from the turbine for the spent fluid from the turbine. The by-pass conduit includes a nozzle which directs the by-passed fluid downwardly at an increased velocity into the discharge conduit for the spent fluid. Also included are a cutting tool, carried by said supporting body, means connected to the turbine to actuate the cutting tool, and means to direct the combined spent fluid and by-passed fluid to the vicinity of the cutting tool for washing away the cuttings, the last named means including means to prevent flow of fluid and cuttings into the apparatus from the cutting tool end.
Notwithstanding the above cited prior art, no reference teaches or suggests the present invention hammer-bit assembly which is self-propelled and which relies upon pressurized air to rotate the hammer-bit assembly.